Magnetopause - Estimating The Standoff Distance To The Magnetopause

Estimating The Standoff Distance To The Magnetopause

If the pressure from particles within the magnetosphere is neglected, it is possible to estimate the distance to the part of the magnetosphere that faces the Sun. The condition governing this position is that the dynamic ram pressure from the solar wind is equal to the magnetic pressure from the Earth's magnetic field.

where and are the density and velocity of the solar wind, and

B(r) is the Magnetic field strength of the planet in SI units (B in T, μ₀ in H/m)

Since the dipole magnetic field strength varies with distance as the magnetic field strength can be written as .

.

Solving this equation for r leads to an estimate of the distance

The distance from Earth to the subsolar magnetopause varies over time due to solar activity, but typical distances range from 6 - 15 R. Empirical models using real-time solar wind data can provide a real-time estimate of the magnetopause location. A bow shock stands upstream from the magnetopause. It serves to decelerate and deflect the solar wind flow before it reaches the magnetopause